Cross Modal (Visual/Auditory) Plasticity

Cross Modal (Visual/Auditory) Plasticity

Buckley and Tobey (2010) examined the relationship between visual and auditory cross-modal plasticity. They compared data from 10 subjects who were pre-lingual cochlear implant (CI) users, to 12 subjects who were post-lingual CI users (mean age across both CI groups = 46 years) to 10 people with normal hearing (mean age 29 years). Of note, all participants had normal or corrected vision of 20/30 or better as verified via Snellen eye chart.

The authors used the visual-evoked potential (N1) amplitude as recorded over the right temporal lobe to partially represent the degree to which cross modal (visual/auditory) plasticity influences speech perception. Of note, the three groups (pre-lingual CI users, post-lingual CI users and normal hearing) were not statistically different with regard to their NI response, with respect to latency (mean = 225 msecs) and amplitude (mean = -0.643microvolts).

In general, as the N1 response amplitude increased, speech perception for the pre-lingual CI group decreased. However, this same relationship was not observed for post-lingual CI users or for normal hearing people. Buckley and Tobey note their results suggest cross modal plasticity is responsible for significant variability for pre-lingual users of CIs, but is not a significant factor for the post-lingual CI group.

Further, the authors suggest the timing (i.e., age of onset of severe-to-profound hearing loss with respect to pre- versus post-lingual) is a more important factor than duration of auditory deprivation prior to obtaining a CI, with respect to cross-modal plasticity.